1. Field of the Invention
This invention pertains generally to microfluidic circuit devices such as optoelectronic tweezers (OET) devices, and more particularly to electrode configuration in such devices.
2. Discussion
Optoelectronic tweezers (OET), dielectrophoresis (DEP), electrowetting, opto-electrowetting (OEW), electroosmosis, and electrophoresis devices are examples of technologies that utilize an electrokinetic mechanism to move particles, such as polystyrene beads, semiconductor microdisks, nanowires, DNA, cells, and liquids or liquid droplets. OET, for example, is a powerful technology that allows for massive parallel manipulation of single cells with light images at low light intensity. Cells are manipulated on an OET platform through light induced dielectrophoresis (DEP), a force exerted on a particle subjected to a non-uniform electric field. OET technology has been used for manipulating many types of particles, including polystyrene beads, semiconductor microdisks, nanowires, DNA, and cells. OEW technology has been used for manipulating liquid droplets on a platform through DEP forces. However, conventional OET and OEW platforms require a sandwich structures consisting of a photoconductive electrode and an ITO electrode for applying voltage. The ITO electrode prohibits OET from being integrated with many microfluidic components for conducting more complex multi-step protocols. On the other hand, Au-mesh electrodes have successfully enabled OET and OEW integration with multilayer PDMS microfluidic devices with valve functions. However, Au-mesh electrodes can withstand only a small amount of deformation and could fail after large deformation that induces cracks on the electrode. To realize OET and OEW integrated microfluidic devices as well as other types of devices that utilize electrokinetic mechanisms (e.g., DEP, electrowetting, opto-electrowetting, electrophoresis, or electroosmosis devices) capable of processing complex functions or to allow microscopic inspection or fluorescence detection, the electrode needs to be transparent, conductive, flexible, and/or capable of bonding strongly to OET, OEW, electrowetting, or DEP chips.